#!/usr/bin/env python # aes.py: implements AES - Advanced Encryption Standard # from the SlowAES project, http://code.google.com/p/slowaes/ # # Copyright (c) 2008 Josh Davis ( http://www.josh-davis.org ), # Alex Martelli ( http://www.aleax.it ) # # Ported from C code written by Laurent Haan ( http://www.progressive-coding.com ) # # Licensed under the Apache License, Version 2.0 # http://www.apache.org/licenses/ """ Modified for py-kms """ import os import math class AES(object): '''AES funtions for a single block. ''' # Very annoying code: all is for an object, but no state is kept! # Should just be plain functions in a AES modlule. #*py-kms* v6 = False # valid key sizes keySize = dict(SIZE_128=16, SIZE_192=24, SIZE_256=32) # Rijndael S-box sbox = [0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16] # Rijndael Inverted S-box rsbox = [0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb, 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e, 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d] def getSBoxValue(self,num): """ Retrieves a given S-Box Value. """ return self.sbox[num] def getSBoxInvert(self,num): """ Retrieves a given Inverted S-Box Value. """ return self.rsbox[num] def rotate(self, word): """ Rijndael's key schedule rotate operation. Rotate a word eight bits to the left: eg, rotate(1d2c3a4f) == 2c3a4f1d Word is an char list of size 4 (32 bits overall). """ return word[1:] + word[:1] # Rijndael Rcon Rcon = [0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb] def getRconValue(self, num): """ Retrieves a given Rcon Value. """ return self.Rcon[num] def core(self, word, iteration): """ Key schedule core.""" # rotate the 32-bit word 8 bits to the left word = self.rotate(word) # apply S-Box substitution on all 4 parts of the 32-bit word for i in range(4): word[i] = self.getSBoxValue(word[i]) # XOR the output of the rcon operation with i to the first part # (leftmost) only word[0] = word[0] ^ self.getRconValue(iteration) return word def expandKey(self, key, size, expandedKeySize): """Rijndael's key expansion. Expands an 128,192,256 key into an 176,208,240 bytes key expandedKey is a char list of large enough size, key is the non-expanded key. """ # current expanded keySize, in bytes currentSize = 0 rconIteration = 1 expandedKey = [0] * expandedKeySize # set the 16, 24, 32 bytes of the expanded key to the input key for j in range(size): expandedKey[j] = key[j] currentSize += size while currentSize < expandedKeySize: # assign the previous 4 bytes to the temporary value t t = expandedKey[currentSize - 4:currentSize] # every 16,24,32 bytes we apply the core schedule to t # and increment rconIteration afterwards if currentSize % size == 0: t = self.core(t, rconIteration) rconIteration += 1 # For 256-bit keys, we add an extra sbox to the calculation if size == self.keySize["SIZE_256"] and ((currentSize % size) == 16): for l in range(4): t[l] = self.getSBoxValue(t[l]) # We XOR t with the four-byte block 16,24,32 bytes before the new # expanded key. This becomes the next four bytes in the expanded key. for m in range(4): expandedKey[currentSize] = expandedKey[currentSize - size] ^ t[m] currentSize += 1 return expandedKey def addRoundKey(self, state, roundKey): """ Adds (XORs) the round key to the state. """ for i in range(16): state[i] ^= roundKey[i] return state def createRoundKey(self, expandedKey, roundKeyPointer): """ Create a round key. Creates a round key from the given expanded key and the position within the expanded key. """ roundKey = [0] * 16 for i in range(4): for j in range(4): roundKey[j * 4 + i] = expandedKey[roundKeyPointer + i * 4 + j] return roundKey def galois_multiplication(self, a, b): """ Galois multiplication of 8 bit characters a and b. """ p = 0 for counter in range(8): if b & 1: p ^= a hi_bit_set = a & 0x80 a <<= 1 # keep a 8 bit a &= 0xFF if hi_bit_set: a ^= 0x1b b >>= 1 return p def subBytes(self, state, isInv): """ Substitute all the values from the state with the value in the SBox using the state value as index for the SBox. """ if isInv: getter = self.getSBoxInvert else: getter = self.getSBoxValue for i in range(16): state[i] = getter(state[i]) return state def shiftRows(self, state, isInv): """ Iterate over the 4 rows and call shiftRow() with that row. """ for i in range(4): state = self.shiftRow(state, i * 4, i, isInv) return state def shiftRow(self, state, statePointer, nbr, isInv): """ Each iteration shifts the row to the left by 1. """ for i in range(nbr): if isInv: state[statePointer:statePointer + 4] = state[statePointer + 3:statePointer + 4] + \ state[statePointer:statePointer + 3] else: state[statePointer:statePointer + 4] = state[statePointer + 1:statePointer + 4] + \ state[statePointer:statePointer + 1] return state def mixColumns(self, state, isInv): """Galois multiplication of the 4x4 matrix. """ # iterate over the 4 columns for i in range(4): # construct one column by slicing over the 4 rows column = state[i:i + 16:4] # apply the mixColumn on one column column = self.mixColumn(column, isInv) # put the values back into the state state[i:i + 16:4] = column return state def mixColumn(self, column, isInv): """ Galois multiplication of 1 column of the 4x4 matrix. """ if isInv: mult = [14, 9, 13, 11] else: mult = [2, 1, 1, 3] cpy = list(column) g = self.galois_multiplication column[0] = g(cpy[0], mult[0]) ^ g(cpy[3], mult[1]) ^ \ g(cpy[2], mult[2]) ^ g(cpy[1], mult[3]) column[1] = g(cpy[1], mult[0]) ^ g(cpy[0], mult[1]) ^ \ g(cpy[3], mult[2]) ^ g(cpy[2], mult[3]) column[2] = g(cpy[2], mult[0]) ^ g(cpy[1], mult[1]) ^ \ g(cpy[0], mult[2]) ^ g(cpy[3], mult[3]) column[3] = g(cpy[3], mult[0]) ^ g(cpy[2], mult[1]) ^ \ g(cpy[1], mult[2]) ^ g(cpy[0], mult[3]) return column def aes_round(self, state, roundKey, roundKms): """ Applies the 4 operations of the forward round in sequence. """ state = self.subBytes(state, False) state = self.shiftRows(state, False) state = self.mixColumns(state, False) #*py-kms* if self.v6: if roundKms == 4: state[0] ^= 0x73 if roundKms == 6: state[0] ^= 0x09 if roundKms == 8: state[0] ^= 0xE4 state = self.addRoundKey(state, roundKey) return state def aes_invRound(self, state, roundKey, roundKms): """ Applies the 4 operations of the inverse round in sequence. """ state = self.shiftRows(state, True) state = self.subBytes(state, True) state = self.addRoundKey(state, roundKey) #*py-kms* if self.v6: if roundKms == 4: state[0] ^= 0x73 if roundKms == 6: state[0] ^= 0x09 if roundKms == 8: state[0] ^= 0xE4 state = self.mixColumns(state, True) return state def aes_main(self, state, expandedKey, nbrRounds): """ Perform the initial operations, the standard round, and the final operations of the forward aes, creating a round key for each round. """ state = self.addRoundKey(state, self.createRoundKey(expandedKey, 0)) i = 1 while i < nbrRounds: state = self.aes_round(state, self.createRoundKey(expandedKey, 16 * i), i) i += 1 state = self.subBytes(state, False) state = self.shiftRows(state, False) state = self.addRoundKey(state, self.createRoundKey(expandedKey, 16 * nbrRounds)) return state def aes_invMain(self, state, expandedKey, nbrRounds): """ Perform the initial operations, the standard round, and the final operations of the inverse aes, creating a round key for each round. """ state = self.addRoundKey(state, self.createRoundKey(expandedKey, 16 * nbrRounds)) i = nbrRounds - 1 while i > 0: state = self.aes_invRound(state, self.createRoundKey(expandedKey, 16 * i), i) i -= 1 state = self.shiftRows(state, True) state = self.subBytes(state, True) state = self.addRoundKey(state, self.createRoundKey(expandedKey, 0)) return state def encrypt(self, iput, key, size): """ Encrypts a 128 bit input block against the given key of size specified. """ output = [0] * 16 # the number of rounds nbrRounds = 0 # the 128 bit block to encode block = [0] * 16 # set the number of rounds if size == self.keySize["SIZE_128"]: nbrRounds = 10 elif size == self.keySize["SIZE_192"]: nbrRounds = 12 elif size == self.keySize["SIZE_256"]: nbrRounds = 14 # *py-kms* The KMS v4 parameters elif size == 20: nbrRounds = 11 else: return None # the expanded keySize expandedKeySize = 16 * (nbrRounds + 1) # Set the block values, for the block: # a0,0 a0,1 a0,2 a0,3 # a1,0 a1,1 a1,2 a1,3 # a2,0 a2,1 a2,2 a2,3 # a3,0 a3,1 a3,2 a3,3 # the mapping order is a0,0 a1,0 a2,0 a3,0 a0,1 a1,1 ... a2,3 a3,3 # # iterate over the columns and over the rows for i in range(4): for j in range(4): block[i + j * 4] = iput[i * 4 + j] # expand the key into an 176, 208, 240 bytes key # the expanded key expandedKey = self.expandKey(key, size, expandedKeySize) # encrypt the block using the expandedKey block = self.aes_main(block, expandedKey, nbrRounds) # unmap the block again into the output for k in range(4): for l in range(4): output[k * 4 + l] = block[k + l * 4] return output def decrypt(self, iput, key, size): """ decrypts a 128 bit input block against the given key of size specified. """ output = [0] * 16 # the number of rounds nbrRounds = 0 # the 128 bit block to decode block = [0] * 16 # set the number of rounds if size == self.keySize["SIZE_128"]: nbrRounds = 10 elif size == self.keySize["SIZE_192"]: nbrRounds = 12 elif size == self.keySize["SIZE_256"]: nbrRounds = 14 #*py-kms* The KMS v4 parameters. elif size == 20: nbrRounds = 11 else: return None # the expanded keySize expandedKeySize = 16 * (nbrRounds + 1) # Set the block values, for the block: # a0,0 a0,1 a0,2 a0,3 # a1,0 a1,1 a1,2 a1,3 # a2,0 a2,1 a2,2 a2,3 # a3,0 a3,1 a3,2 a3,3 # the mapping order is a0,0 a1,0 a2,0 a3,0 a0,1 a1,1 ... a2,3 a3,3 # iterate over the columns and the rows for i in range(4): for j in range(4): block[i + j * 4] = iput[i * 4 + j] # expand the key into an 176, 208, 240 bytes key expandedKey = self.expandKey(key, size, expandedKeySize) # decrypt the block using the expandedKey block = self.aes_invMain(block, expandedKey, nbrRounds) # unmap the block again into the output for k in range(4): for l in range(4): output[k * 4 + l] = block[k + l * 4] return output class AESModeOfOperation( object ): '''Handles AES with plaintext consistingof multiple blocks. Choice of block encoding modes: OFT, CFB, CBC ''' # Very annoying code: all is for an object, but no state is kept! # Should just be plain functions in an AES_BlockMode module. aes = AES() # structure of supported modes of operation modeOfOperation = dict(OFB=0, CFB=1, CBC=2) # converts a 16 character string into a number array def convertString(self, string, start, end, mode): if end - start > 16: end = start + 16 if mode == self.modeOfOperation["CBC"]: ar = [0] * 16 else: ar = [] i = start j = 0 while len(ar) < end - start: ar.append(0) while i < end: ar[j] = ord(string[i]) j += 1 i += 1 return ar def encrypt(self, stringIn, mode, key, size, IV): """ Mode of Operation Encryption stringIn - Input String mode - mode of type modeOfOperation hexKey - a hex key of the bit length size size - the bit length of the key hexIV - the 128 bit hex Initilization Vector """ if len(key) % size: return None if len(IV) % 16: return None # the AES input/output plaintext = [] iput = [0] * 16 output = [] ciphertext = [0] * 16 # the output cipher string cipherOut = [] # char firstRound firstRound = True if stringIn != None: for j in range(int(math.ceil(float(len(stringIn))/16))): start = j * 16 end = j * 16 + 16 if end > len(stringIn): end = len(stringIn) plaintext = self.convertString(stringIn, start, end, mode) if mode == self.modeOfOperation["CFB"]: if firstRound: output = self.aes.encrypt(IV, key, size) firstRound = False else: output = self.aes.encrypt(iput, key, size) for i in range(16): if len(plaintext) - 1 < i: ciphertext[i] = 0 ^ output[i] elif len(output) - 1 < i: ciphertext[i] = plaintext[i] ^ 0 elif len(plaintext) - 1 < i and len(output) < i: ciphertext[i] = 0 ^ 0 else: ciphertext[i] = plaintext[i] ^ output[i] for k in range(end - start): cipherOut.append(ciphertext[k]) iput = ciphertext elif mode == self.modeOfOperation["OFB"]: if firstRound: output = self.aes.encrypt(IV, key, size) firstRound = False else: output = self.aes.encrypt(iput, key, size) for i in range(16): if len(plaintext) - 1 < i: ciphertext[i] = 0 ^ output[i] elif len(output) - 1 < i: ciphertext[i] = plaintext[i] ^ 0 elif len(plaintext) - 1 < i and len(output) < i: ciphertext[i] = 0 ^ 0 else: ciphertext[i] = plaintext[i] ^ output[i] for k in range(end - start): cipherOut.append(ciphertext[k]) iput = output elif mode == self.modeOfOperation["CBC"]: for i in range(16): if firstRound: iput[i] = plaintext[i] ^ IV[i] else: iput[i] = plaintext[i] ^ ciphertext[i] firstRound = False ciphertext = self.aes.encrypt(iput, key, size) # always 16 bytes because of the padding for CBC for k in range(16): cipherOut.append(ciphertext[k]) return mode, len(stringIn), cipherOut def decrypt(self, cipherIn, originalsize, mode, key, size, IV): """ Mode of Operation Decryption cipherIn - Encrypted String originalsize - The unencrypted string length - required for CBC mode - mode of type modeOfOperation key - a number array of the bit length size size - the bit length of the key IV - the 128 bit number array Initilization Vector """ if len(key) % size: return None if len(IV) % 16: return None # the AES input/output ciphertext = [] iput = [] output = [] plaintext = [0] * 16 # the output plain text character list chrOut = [] # char firstRound firstRound = True if cipherIn != None: for j in range(int(math.ceil(float(len(cipherIn))/16))): start = j * 16 end = j * 16 + 16 if end > len(cipherIn): end = len(cipherIn) ciphertext = cipherIn[start:end] if mode == self.modeOfOperation["CFB"]: if firstRound: output = self.aes.encrypt(IV, key, size) firstRound = False else: output = self.aes.encrypt(iput, key, size) for i in range(16): if len(output) - 1 < i: plaintext[i] = 0 ^ ciphertext[i] elif len(ciphertext) - 1 < i: plaintext[i] = output[i] ^ 0 elif len(output) - 1 < i and len(ciphertext) < i: plaintext[i] = 0 ^ 0 else: plaintext[i] = output[i] ^ ciphertext[i] for k in range(end - start): chrOut.append(chr(plaintext[k])) iput = ciphertext elif mode == self.modeOfOperation["OFB"]: if firstRound: output = self.aes.encrypt(IV, key, size) firstRound = False else: output = self.aes.encrypt(iput, key, size) for i in range(16): if len(output) - 1 < i: plaintext[i] = 0 ^ ciphertext[i] elif len(ciphertext) - 1 < i: plaintext[i] = output[i] ^ 0 elif len(output) - 1 < i and len(ciphertext) < i: plaintext[i] = 0 ^ 0 else: plaintext[i] = output[i] ^ ciphertext[i] for k in range(end - start): chrOut.append(chr(plaintext[k])) iput = output elif mode == self.modeOfOperation["CBC"]: output = self.aes.decrypt(ciphertext, key, size) for i in range(16): if firstRound: plaintext[i] = IV[i] ^ output[i] else: plaintext[i] = iput[i] ^ output[i] firstRound = False if originalsize is not None and originalsize < end: for k in range(originalsize - start): chrOut.append(chr(plaintext[k])) else: for k in range(end - start): chrOut.append(chr(plaintext[k])) iput = ciphertext return "".join(chrOut) def append_PKCS7_padding(s): """ Return s padded to a multiple of 16-bytes by PKCS7 padding. """ numpads = 16 - (len(s)%16) return s + numpads*chr(numpads) def strip_PKCS7_padding(s): """ Return s stripped of PKCS7 padding. """ if len(s)%16 or not s: raise ValueError("String of len %d can't be PCKS7-padded" % len(s)) numpads = ord(s[-1]) if numpads > 16: raise ValueError("String ending with %r can't be PCKS7-padded" % s[-1]) return s[:-numpads] def encryptData(key, data, mode=AESModeOfOperation.modeOfOperation["CBC"]): """ Encrypt `data` using `key` `key` should be a string of bytes. returned cipher is a string of bytes prepended with the initialization vector. """ key = map(ord, key) if mode == AESModeOfOperation.modeOfOperation["CBC"]: data = append_PKCS7_padding(data) keysize = len(key) assert keysize in AES.keySize.values(), 'invalid key size: %s' % keysize # create a new iv using random data iv = [ord(i) for i in os.urandom(16)] moo = AESModeOfOperation() (mode, length, ciph) = moo.encrypt(data, mode, key, keysize, iv) # With padding, the original length does not need to be known. It's a bad # idea to store the original message length prepend the iv. return ''.join(map(chr, iv)) + ''.join(map(chr, ciph)) def decryptData(key, data, mode=AESModeOfOperation.modeOfOperation["CBC"]): """ Decrypt `data` using `key` `key` should be a string of bytes. `data` should have the initialization vector prepended as a string of ordinal values. """ key = map(ord, key) keysize = len(key) assert keysize in AES.keySize.values(), 'invalid key size: %s' % keysize # iv is first 16 bytes iv = map(ord, data[:16]) data = map(ord, data[16:]) moo = AESModeOfOperation() decr = moo.decrypt(data, None, mode, key, keysize, iv) if mode == AESModeOfOperation.modeOfOperation["CBC"]: decr = strip_PKCS7_padding(decr) return decr def generateRandomKey(keysize): """ Generates a key from random data of length `keysize`. The returned key is a string of bytes. """ if keysize not in (16, 24, 32): emsg = 'Invalid keysize, %s. Should be one of (16, 24, 32).' raise ValueError, emsg % keysize return os.urandom(keysize) def testStr(cleartext, keysize=16, modeName = "CBC"): """ Test with random key, choice of mode. """ print 'Random key test', 'Mode:', modeName print 'cleartext:', cleartext key = generateRandomKey(keysize) print 'Key:', [ord(x) for x in key] mode = AESModeOfOperation.modeOfOperation[modeName] cipher = encryptData(key, cleartext, mode) print 'Cipher:', [ord(x) for x in cipher] decr = decryptData(key, cipher, mode) print 'Decrypted:', decr if __name__ == "__main__": moo = AESModeOfOperation() cleartext = "This is a test with several blocks!" cipherkey = [143, 194, 34, 208, 145, 203, 230, 143, 177, 246, 97, 206, 145, 92, 255, 84] iv = [103, 35, 148, 239, 76, 213, 47, 118, 255, 222, 123, 176, 106, 134, 98, 92] mode, orig_len, ciph = moo.encrypt(cleartext, moo.modeOfOperation["CBC"], cipherkey, moo.aes.keySize["SIZE_128"], iv) print 'm=%s, ol=%s (%s), ciph=%s' % (mode, orig_len, len(cleartext), ciph) decr = moo.decrypt(ciph, orig_len, mode, cipherkey, moo.aes.keySize["SIZE_128"], iv) print decr testStr(cleartext, 16, "CBC")